EU warns it is prepared to react to US president's steep tariffs on steal and aluminium imports.

Several industry trade groups have warned that the newly imposed steep tariffs on steel and aluminium imports to the United States could prompt a trade war.

In a controversial move on Thursday, Trump imposed steep tariffs of 25 percent for steel and 10 percent for aluminium imports to the US.

The trade sanctions will come into force in two weeks' time. Trump temporarily exempted its North American neighbours, Canada and Mexico, from the newest measures.

Trump signed proclamations at a ceremony at the White House while surrounded by steelworkers.

"A strong steel and aluminum industry are vital to our national security, absolutely vital," he said. "Steel is steel. If you don't have steel, you don't have a country.

"Our industries have been targeted for years and years - decades, in fact - by unfair foreign trade practices leading to the shuttered plants and mills, the laying-off of millions of workers and the decimation of entire communities. And that's going to stop."

Trump said the "aggressive" foreign trade amounted to an "assault" on the US, but that he would also show flexibility with friendly countries, possibly removing tariffs for some.

Trump also indicated that military allies, including NATO countries that spend at least two percent of gross domestic product on defence, could see a reduction in these tariffs.

Analysts have called the justification "an absurdity".

Trade War

Several industry trade groups warned that the tariffs could prompt a trade war, without resolving problems they intend to address.

Axel Eggert, chief of Europe's main steel federation (EUROFER) said on Friday that Trump's tariffs are absurd, and, with the expected massive steel import surge to the European Union (EU), they could cost tens of thousands of jobs across the continent.

The EU produces 177 million tonnes of steel and exports around 5 million tonnes of steel to the US every year, a small share, overall.

The European Commission had already warned on Wednesday that if the US went ahead with its plan, it would retaliate with increased tariffs on American goods such as Bourbon whiskey, Levis jeans, Florida orange juice and peanut butter.

The retaliatory hit list of 100 American products amounts to $3.5bn. It also said that it would take the case to the World Trade Organization (WTO) in an attempt to get the tariffs ruled as unlawful. It will also add safeguarding measures and put its own tariffs in place to prevent an excess of steel imports to the marketplace.

The EU's trade chief Cecilia Malmstrom warned on Friday, at a panel discussion in Brussels, that imposing tariffs is not the way to resolve overcapacity in the steel sector.

"Whereas we share the concerns over overcapacity in the steel sector, this is not the right way to deal with it," Malmstrom said.

"And it is certainly not the right way to include Europe in that because we are friends, we are allies, we work together, we cannot possibly be a threat to national security in the US, so we are counting on being excluded."

Despite objections by many business trade groups, by most Democrats and Republicans, and by a number of advisers in the Trump administration, the US president forged ahead with his plan on Thursday, keeping a promise he made during his 2016 presidential campaign.